FRACTOGRAPHIC OBSERVATIONS ON A HIGHLY IRRADIATED AISI 304 STEEL AFTER CONSTANT LOAD TESTS IN SIMULATED PWR WATER AND ARGON AND AFTER SUPPLEMENTARY TENSILE AND IMPACT TESTS

摘要

Intergranular cracking has been observed in highly irradiated AISI 304 following constant load tests at 340 ℃ in both simulated PWR water and, to a lesser extent, argon. Complementary investigations to clarify the mechanical behavior of the irradiated steel were performed. Those investigations consisted of tensile tests in air at room temperature and at 300 ℃, and impact testing in air at room and liquid nitrogen temperatures. The prevailing fracture mode for the irradiated material was ductile-dimple at 300 ℃ (using a strain rate of 1·10~(-3) s~(-1)) and intergranular at room temperature and below. The results of the investigations show that the irradiated stainless steel studied is susceptible to intergranular fracture without environmental assistance. The results are discussed based on the possible influences of strain rate, temperature and environment on the fracture mode in highly irradiated stainless steels.